fix(cli): detect Windows Yarn global installs in update notices

[WenJing95]

Summary

On Windows, Yarn Classic puts global packages under %LOCALAPPDATA%\Yarn\Data\global, which updateCommand doesn't recognize. The update notice then suggests npm install @openai/codex-security@latest without -g, which doesn't update the global CLI.

Changes

updateCommand now treats /yarn/data/global/ as a global Yarn install and suggests yarn global add. Added a Windows row to the install-path test.

Testing

Tests pass.

Risk and rollout

Other install paths get the same command as before.

Public disclosure review

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